Not included in this review: Osteopathic manipulative therapy, mobilization, mobilization therapy, physical therapy. Traction is a physical modality used primarily in physical therapy, and is inconsistently utilized in chiropractic offices.

Overview: Chiropractic is a health care discipline that focuses on the relationship between musculoskeletal structure (primarily the spine) and body function (as coordinated by the nervous system), and how this relationship affects the preservation and restoration of health. The broad term "spinal manipulative therapy" incorporates all types of manual techniques, including chiropractic.

History: Spinal manipulation was used medicinally as early as 2700 B.C. in ancient Chinese medicine. Hippocrates and Galen used manipulative techniques, and the word "chiropractic" is derived from Greek chiropraktikos, meaning "effective treatment by hand."

In the late 1800s, David Daniel Palmer systematized the principles upon which modern chiropractic is based, suggesting that abnormal nerve function is the primary cause of disorders, and recommending adjustment of the spine as an effective therapy. The Palmer School of Chiropractic opened in 1895, and one-third of students were physicians. Acceptance of Palmer's principles in the medical community varied, and some early chiropractors were imprisoned (including Palmer himself). A schism between chiropractors and medical doctors persisted, and between 1977-1987, an antitrust lawsuit was brought against the American Medical Association for systematic bias against the chiropractic profession (which was ultimately successful).

Divisions existed within the chiropractic community as well, and during the early 20th century, two schools of thought emerged: One group ("straights") asserted that subluxation is the underlying cause of disease. A second group ("mixers") worked in a multidisciplinary setting with physicians, and accepted other pathophysiologic theories of disease. Two different chiropractic associations were founded between 1920-1926 reflecting this division: the International Chiropractic Association (ICA) and the American Chiropractic Association (ACA), respectively.

In 1972, chiropractic treatment became reimbursable by Medicare. In 1974, nationally recognized standards were adopted by the Council on Chiropractic Education (CCE), and were recognized by the U.S. Department of Education. All U.S. chiropractic colleges achieved accreditation by the CCE by 1975. Currently, all 50 U.S. states have statutes recognizing and regulating the practice of chiropractic.

Currently: In the United States, chiropractors are the most frequently used non-physician primary health providers, after dentists (1;2). There are more than 60,000 licensed American chiropractors (3), a number expected to reach 100,000 by 2010 (4). Almost 80% of all visits to chiropractors are for musculoskeletal complaints (5), and more than 40% are for back pain (6). In 1999, 11% of adults and more than 30% of patients with low back pain visited a chiropractor (7). For two-thirds of patients, a chiropractor was the only provider seen for these complaints (8).

The cost effectiveness of chiropractic care remains controversial and is not clearly established (9-12).

Techniques: There are more than 100 distinct chiropractic and spinal manipulative adjusting techniques, and there is variability between practitioners. Some approaches use highly specialized tables or hand-held equipment. Techniques that are widely taught in chiropractic schools include: Diversified, Extremity Adjusting, Activator, Gonstead, Cox Flexion-Distraction, and Thompson. Other techniques are taught on chiropractic campuses outside of the established curriculum, and many are taught in seminars that are not sanctioned as a part of the established chiropractic curriculum. Categories of therapeutic approaches include the following:

Manipulation: A primary chiropractic therapeutic application that involves applying a specific amount of force vectored through a specific plane of motion of a spinal or peripheral joint, in order to reduce joint restriction and facilitate normal range of motion. Long-lever manipulation uses the femur, shoulder, head, or pelvis to affect larger sections of the spine in a non-specific manner. Specific short lever, dynamic thrusts utilize a specific contact on a transverse spinous process of vertebra, muscle, or ligament. Point pressure manipulation includes the gouging or manual stimulation of specific points without attempting to actually massage a muscle or move a joint.

Mechanical traction: A technique that incorporates the use of an external system of applied resistance to facilitate joint decompression of the spine or extremity. Manual traction is often performed on a segment of the spine without attempting to mobilize the joint through a specific passive movement.

Massage/soft tissue mobilization: A category of soft tissue therapeutic techniques used to reduce muscle spasm, soreness, or tightness. These procedures are directed at the subcutaneous, muscular, or tendinous tissues and do not result in significant joint movement. Example techniques include myofascial trigger point therapy, cross friction massage, active release therapy, muscle stripping, and rolfing. Mobilization or articulation technique uses slow rhythmic movements rather than quick sharp thrusts, and may be performed within the passive range of motion of the spine.

Electrical muscle stimulation (EMS)/interferential therapy: A therapeutic modality using two medium-frequency currents that intersect. The intersecting current is believed by some practitioners to reduce muscle spasm and pain.

There are traditional and scientifically-based hypotheses regarding the mechanism of action of chiropractic and spinal manipulation. There is overlap between some of these theories, with research in several areas. However, the physiologic mechanism of spinal manipulation remains largely unknown.

Traditional theories: The vertebral subluxation hypothesis proposes that alterations in normal anatomical/physiologic relationships between contiguous articular structures result in disease, and that chiropractic/manipulative methods can reduce these positional abnormalities (13-18). "Vitalism" is the concept that the body has the innate ability to heal itself if relieved of spinal irritations or subluxations (19). Correction of subluxations has been suggested to restore the flow of life force throughout the body, resulting in a brief convalescence and a return to optimum health (20;21). There is limited scientific evidence in these areas (22;23).

The nerve compression hypothesis suggests that intervertebral subluxations can cause irritation or compression of spinal nerve roots and interfere with nerve transmission (14). The fixation hypothesis proposes that vertebral muscles become locked and lose range of motion, leading to the release of neurotoxic mediators and abnormal nerve conduction (24;25). The axoplasmic aberration hypothesis asserts that compression of spinal nerves or nerve roots may hinder axoplasmic transport and damage nerves.

It has been proposed that chiropractic may reduce nerve impingement at intervertebral foramina (26), alter the distribution of loads between joints (27-30), create gaps between joints and break up fibrous adhesions that interfere with normal function (31), improve range of motion (32-35), improve immune function (36;37); and foster healing through the clinician-patient relationship (20;38-43).

Scientific research: Animal experiments report that vertebral displacement may alter the function of nerves arising from intervertebral muscles and influence heart rate and blood pressure (44-46). Human studies report possible changes in patterns of nerve conduction and reflexes during spinal manipulation, although the evidence is not definitive (47-62). Reduced sensitivity to painful stimuli has been reported in some studies of spinal manipulation (63-68), but not in others (69). Some studies report elevated plasma levels of substance P (70;71) and endorphins (72-77) following spinal manipulation, although other research reports no effects (78-80).

Problems in chiropractic research: Because spinal manipulation involves the hands-on application of a physical therapy, blinding in studies presents a challenge. Often, the effects of treatment are evaluated by those administering therapy. These individuals are not blinded to the type of treatment being administered (unlike assessors in pharmacologic studies in which active and placebo drugs are similar in appearance). This is a potential source of bias. Similarly, placebo control is difficult, and necessitates the use of "sham manipulation" (81). Existing studies are difficult to compare with each other, because methods of manipulation vary between trials, and definitions of medical conditions/diagnoses are inconsistent. Most research has used non-standardized, subjective outcome measures that cannot be pooled.

These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.

GRADE *

The use of spinal manipulative therapy for the relief of tension or migraine headache has been reported in several controlled human trials (82-92), systematic reviews (93-96), and case reports (97-105). Overall, the quality of studies is not high, with incomplete reporting of design, inconsistent use of techniques between studies, and variable results. Despite these methodologic problems, overall the evidence suggests some benefits in the prevention of episodic tension headache. Effects on migraine headache have not been demonstrated. Better quality research is necessary in this area before a firm conclusion can be drawn.

Patients should be aware of the safety concerns surrounding cervical/neck manipulation before starting this type of therapy.

B

There are more than 150 published human trials and case reports that detail the use of chiropractic manipulation in patients with low back pain. Results are variable, with some studies reporting benefits, and others suggesting no significant effects. Most trials are not well designed or reported, with inconsistent use of definitions of disease, techniques, and measured outcomes. Several analyses (meta-analyses) have attempted to pool the results of the better-quality trials (106-120). However, combining or comparing results of different trials is difficult due to inconsistencies between studies, and these meta-analyses have also reported variable effects. Despite these problems with existing research, the available scientific evidence overall suggests some improvement in pain symptoms. Better research is necessary before a definitive conclusion can be reached.

B

There is not enough reliable scientific evidence to conclude whether chiropractic techniques are beneficial in the management of acute back pain when compared to other approaches, including conservative management (121-129).

C

There is not enough reliable scientific evidence to conclude the effects of chiropractic techniques in the management of migraine headache. There is limited human evidence in this area (97;100;103;130-135).

C

Multiple studies have examined the effects of spinal manipulation in patients with herniated lumbar discs (136-147). Results are variable, with some studies reporting benefits, and others finding no effects. Various techniques, measurement systems, and study designs have been used, and overall the quality of studies has been poor. Better quality research is necessary before a firm conclusion can be drawn.

C

Multiple studies have examined the effects of spinal manipulation in patients with acute or chronic neck pain (148-162). Overall, the quality of studies has been poor, and reviews of this topic have been unable to form clear or convincing conclusions due to variability between studies and methodologic weaknesses (163-170). Cervical spine manipulation and mobilization appear to have equal effects (171;172). Better quality research is necessary before a firm conclusion can be drawn.

C

Several studies report the effects of chiropractic spinal manipulative therapy on breathing indices and quality of life in children and adults with asthma (173-180). Results are variable, and in the studies with positive results, mostly subjective but not objective (lung function test) changes are reported. Due to methodologic problems and variable results, no clear conclusions can be drawn in this area.

C

There is not enough reliable scientific evidence to conclude the effects of chiropractic techniques in the management of carpal tunnel syndrome (181-184). Early evidence and some experts suggest that chiropractic manipulation may be as effective as conservative treatments such as anti-inflammatory drugs or splinting.

C

There is not enough reliable scientific evidence to conclude the effects of chiropractic techniques in the management of cervical disc herniation (185;186).

C

There is not enough reliable scientific evidence to conclude the effects of chiropractic techniques in the management of COPD (187-189).

C

There is not enough reliable scientific evidence to conclude the effects of chiropractic techniques in the management of chronic pelvic pain (CPP) (190-194).

C

There is not enough reliable scientific evidence to conclude the effects of chiropractic techniques in the management of duodenal ulcer (195).

C

There is not enough reliable scientific evidence to conclude the effects of chiropractic techniques in the management of dysmenorrhea (196-201).

C

There is not enough reliable scientific evidence to conclude the effects of chiropractic techniques in the management of fibromyalgia (202-205).

C

The effects of spinal manipulative techniques on blood pressure remain controversial. It has been hypothesized that nervous system effects of spinal manipulation can lower both systolic and diastolic pressure. Numerous trials, reviews, and commentaries have been published in this area (206-220). Although some studies are suggestive, overall the existing evidence remains indeterminate due to methodologic weaknesses and variability between studies. Better research is necessary before a firm conclusion can be drawn.

Nevertheless, caution should be used in patients with low blood pressure or taking medications that may lower blood pressure further.

C

There is not enough reliable scientific evidence to conclude the effects of chiropractic techniques on CD4 count or quality of life in patients with HIV/AIDS (221).

C

There is not enough reliable scientific evidence to conclude the effects of chiropractic techniques in the management of infantile colic (222-228).

C

There is not enough reliable scientific evidence to conclude the effects of chiropractic techniques in the management of jet lag, and preliminary evidence suggests a lack of benefit (229).

C

There is not enough reliable scientific evidence to conclude the effects of chiropractic techniques in the management of nocturnal enuresis (230-233).

C

There is not enough reliable scientific evidence to conclude the effects of chiropractic techniques in the management of otitis media in children (234-236).

C

There is not enough reliable scientific evidence to conclude the effects of chiropractic techniques in the management of Parkinson's disease (237;238).

C

There is not enough reliable scientific evidence to conclude the effects of chiropractic techniques in the management of phobias (239-241).

C

There is not enough reliable scientific evidence to conclude the effects of chiropractic techniques in the management of pneumonia in the elderly (242).

C

There is not enough reliable scientific evidence to conclude the effects of chiropractic techniques in the management of premenstrual syndrome (243;244).

C

There is not enough reliable scientific evidence to conclude the effects of chiropractic techniques for respiratory tract infections (245-248).

C

There is not enough reliable scientific evidence to conclude the effects of chiropractic techniques in the management of seizure disorder (249).

C

There is not enough reliable scientific evidence to conclude the effects of chiropractic techniques for shoulder pain, frozen shoulder, or rotator cuff injuries (250-255).

C

There is not enough reliable scientific evidence to conclude the effects of chiropractic techniques in the management of ankle inversion sprains (256).

C

There is not enough reliable scientific evidence to conclude the effects of chiropractic techniques in the management of TMJ (257-261)

C

There is not enough reliable scientific evidence to conclude the effects of chiropractic techniques for the recovery or prevention of visual field narrowing (262-267).

C

Despite promising preliminary results, there is not enough reliable scientific evidence to conclude the effects of chiropractic techniques for the improvement of symptoms related to whiplash injuries (268-272).

C

* Key to grades

A: Strong scientific evidence for this useB: Good scientific evidence for this useC: Unclear scientific evidence for this useD: Fair scientific evidence for this use (it may not work)F: Strong scientific evidence against this use (it likley does not work)

Tradition / Theory
The below uses are based on tradition, scientific theories, or limited research. They often have not been thoroughly tested in humans, and safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider. There may be other proposed uses that are not listed below.

Safety
Many complementary techniques are practiced by healthcare professionals with formal training, in accordance with the standards of national organizations. However, this is not universally the case, and adverse effects are possible. Due to limited research, in some cases only limited safety information is available.

General:

There are many reports of serious complications during and after spinal manipulation (particularly with cervical spine/neck manipulation). However, the frequency of these events remains controversial and unclear. The most common adverse effect is believed to be local discomfort in the area of treatment (297-299), although most concern centers around the less common but potentially life-threatening risks of stroke/vertebral artery dissection, and spinal cord/nerve damage. Deaths have been reported (300). Some researchers and practitioners blame poor technique, and others believe that the use of high-velocity forceful rotational (twisting) motions of the head increase the risk of serious complications, and suggest using lower-velocity/force non-rotational motion (301-305).

Frequency of adverse effects:

Because there is not a systematic surveillance system or a reliable large prospective study, the true prevalence of side effects due to spinal manipulation is not known (306). Estimates of the frequency of adverse effects range from 0.2-0.5% (307-310), with serious complications such as stroke occurring in 1-5 out of every 100,000 patients undergoing neck manipulation (311-318), or some estimates at fewer than 1 in a million (319-324). However, other authors believe that these events are much more common. Recent research suggests that the odds of experiencing a stroke/dissection after cervical spine manipulation may be more that six times greater than in people who do not undergo manipulation (325-327).

Lower back manipulation is generally regarded as being safer than neck (cervical spine) manipulation (328). Some authors suggest that chiropractic manipulation is safer than treatment with non-steroidal anti-inflammatory drugs (329), spine surgery (330), or hospitalization (331), although these areas are not well studied.

There are several possible causes of inaccuracies in estimates of prevalence. If people seek spinal manipulation for relief of symptoms related to underlying conditions that are the true causes of complications such as stroke, over-reporting of stroke due to manipulation would occur (324;332-340). In contrast, much higher rates of adverse effects have been proposed as being due to under-reporting (341-347). Collections of adverse event reports by professional organizations in the Unites States, Europe, and Australia have brought further attention to the serious risks associated with spinal manipulation (318;346;348-351).

Pre-treatment screening:

It is unclear if there is an increased risk of adverse events in patients with preexisting abnormalities of blood vessels in the neck or brainstem, which potentially could be identified with pre-treatment questioning or imaging tests (352-354). Pre-treatment screening with cervical spine extension-rotation to assess for symptoms does not appear to be effective (355-358). Other attempts at pre-treatment testing to identify at-risk individuals have not been clearly successful (359-362).

Reported adverse effects:

Stroke & vertebrobasilar/carotid artery dissection: There are many cases of stroke and arterial dissection following cervical manipulation reported in the medical and legal literature, often occurring in young individuals (20 to 60 years old) (315;333;363-393). Ischemic stroke may occur immediately during or after the procedure, with possible conversion to hemorrhagic stroke. Symptoms may not appear until several days or weeks later, based on reported cases. Various parts of the brain have been affected, including brainstem, cerebellum, occipital, parietal, and frontal lobes. Residual neurologic deficits may remain long-term (307;315;394-449).

These events are most often associated with vertebral artery dissection, a process that involves an expanding hematoma (blood collection or clot) within the wall of the blood vessel or blockage of the blood vessel by a small flap of vessel wall that develops due to trauma during neck manipulation movements. Carotid artery dissection and thrombosis have also been reported with neck manipulation (365;460-463). Involvement of the basilar and cerebral arteries is also reported (464-467).

Anticoagulant (blood-thinning) therapy: Thoracic spinal hemorrhage after manipulation has been reported with the use of the anticoagulant ("blood thinning") drug warfarin (Coumadin®) (507). Patients with blood clotting disorders or taking anticoagulant therapies may be at increased risk of adverse effects such as spinal bleeding following manipulative therapy.

Musculoskeletal: There are reports of muscle strains, sprains, and spasm following chiropractic manipulation, although it is not clear if these problems were actually related to the therapy, or were preexisting conditions (508;509). Osteomyelitis (bone infection) in the spine has been reported, although chiropractic was likely not the cause, but rather was sought as a therapy due to pain related to infection (510).

Blood pressure effects: The effects of spinal manipulative techniques on blood pressure remain controversial. It has been hypothesized that nervous system effects of spinal manipulation can lower both systolic and diastolic pressure. Numerous trials, reviews, and commentaries have been published in this area (209;217;218;511-521). Although some studies are suggestive, overall the existing evidence remains indeterminate due to methodologic weaknesses and variability between studies. Better research is necessary before a firm conclusion can be drawn.

Radiation exposure: Some authors suggest that exposure to radiation during x-rays ordered by chiropractors may pose a health risk, since approximately 96% of new U.S. patients and 80% of follow-up patients undergo x-rays (72% in Europe) (522). Although the amount of radiation from plain x-rays is generally considered to be small, regular use of x-rays may increase the risk of some types of cancer.

Tracheal damage: Prior surgery of the trachea ("windpipe") or tracheostomy may increase the risk of tracheal rupture during neck manipulation (523).

Cardiovascular complications: There is a report of a heart attack which occurred in a 38-year-old man during cervical spine manipulation (524). It is not clear if manipulation played a causative role in this event.

Underlying conditions that may increase risk:

Patients with existing blood vessel aneurysms (such as abnormalities in brain blood vessels or aortic aneurysms), atherosclerotic disease ("hardening" of the arteries, including carotid artery disease), collagen disorders, vasculitis, other underlying blood vessel abnormalities, or collagen vascular diseases (such as systemic lupus erythematosus) may be at increased risk of stroke or blood vessel dissection (525;526). Individuals with osteomyelitis (bone infection) (527), cancer involving bone (502), vertebral fractures, severe degenerative joint disease (osteoarthritis), osteoporosis, and ankylosing spondylitis may be at increased risk of fracture or spinal damage leading to nerve disorders or spinal cord damage (528-530). Prior surgery of the trachea or tracheostomy may increase the risk of tracheal rupture (531). Underlying tumors of the brain or near the spinal cord may result in adverse outcomes such as tumor rupture or delayed diagnosis (532-537). Patients with blood clotting disorders or taking anticoagulant ("blood thinning") therapies such as warfarin (Coumadin®) may be at increased risk of adverse effects such as spinal bleeding following manipulative therapy (538). Caution should be used in patients with low blood pressure or taking medications that may lower blood pressure further due to inconclusive reports of lowered blood pressure with the use of manipulative techniques (209;217;218;539-549). Neck pain following cervical manipulation may be a warning sign for stroke (550;551).

Delayed diagnosis/additional care:

Use of spinal manipulation for symptoms/conditions should not delay the time to diagnosis or treatment with more proven methods. Individuals who experience persistent symptoms or develop neck pain after manipulation should seek further medical attention without delay, as this may be a warning sign for stroke (532;552-557). Patients are advised to discuss spinal manipulation/chiropractic with a primary healthcare provider before starting treatment.

The information in this monograph is intended for informational purposes only, and is meant to help users better understand health concerns. Information is based on review of scientific research data, historical practice patterns, and clinical experience. This information should not be interpreted as specific medical advice. Users should consult with a qualified healthcare provider for specific questions regarding therapies, diagnosis and/or health conditions, prior to making therapeutic decisions.